Putting in an irrigation system: what to sort before you dig

What an irrigation install involves

An installer designs the system to your garden, then trenches in the pipework, fits drip lines for beds and pop-up sprinklers for lawns, wires up a controller and connects it all to the water supply. Zoning is the craft of it — grouping areas with similar water needs so beds and lawn each get the right amount rather than a compromise that suits neither.

Trenching is where the labour goes: soft garden soil is quick, while cutting through established lawn, clay or around paving is slow. The connection to mains water needs a backflow prevention device, and that part is licensed plumbing — a proper installer either holds the ticket or brings in a plumber to fit and certify it, protecting your drinking water from any back-siphon.

How the cost works

Irrigation is priced by the area covered and the type of system. Drip lines for garden beds are the cheapest to run and install, pop-up sprinklers for lawns cost more, and a fully automated multi-zone system with a smart controller sits at the top. Most residential systems land in a mid-range band, with larger or more complex gardens climbing from there.

The variables that move the price are the number of zones, the controller's sophistication, and how hard the trenching is — established lawn and clay slow the job, soft beds speed it up. The backflow device and any plumbing connection add cost but aren't optional. Treat figures as indicative; a site visit that assesses your soil, layout and water pressure produces the real number.

Choosing an installer

Irrigation installation itself is largely an unlicensed garden trade, so judge on design thinking and track record — ask how they'd zone your garden and why, since good zoning is what separates an efficient system from a wasteful one. Photos of installed controllers and pop-ups tell you little; the reasoning behind the layout tells you a lot.

The one hard licensing point is the water connection. The backflow prevention device that stops garden water siphoning back into the mains must be fitted and certified by a licensed plumber in every state. Ask directly how the mains connection and backflow are handled, and make sure that certification is part of the quote rather than a corner quietly cut.

Mistakes to avoid

Irrigation problems usually trace back to design shortcuts or a skipped compliance step — a system that waters unevenly because it was under-zoned, or a mains connection done without the backflow protection the law requires. Both are avoidable at the quoting stage.

• Accepting a system with too few zones, so beds and lawn get the same water
• Letting anyone unlicensed do the mains connection and backflow device
• Not accounting for your water pressure, which limits how many sprinklers a zone can run
• Skipping a smart or rain-sensing controller, then watering through downpours
• Choosing on price without understanding how the garden was zoned
• Forgetting to locate and mark the buried lines before any later digging